Electric Resistance Efficiency
Electric resistance heating is generally considered to be 100% efficient. That's because almost all of the electricity put into a resistance heater comes out as heat.
The misconception that sometimes traps and confuses people is thinking that this is the entire story, and forgetting that making the electricity and getting it to the heater was not 100% efficient. If you take into account the efficiency losses of the power plant where the electricity was produced, and the losses that take place as it travels through the distribution system, resistance heat is far less efficient.